Aqueous dispersions useful for primer coatings

Abstract

Aqueous dispersions which comprise an emulsion polymer which is stable with respect to polyvalent zirconium ions, and a water-soluble zirconium compound, prevent the penetration of constituents from substrates which show a tendency to bleeding, and the dispersions are therefore suitable as a primer, especially for woods.

What is claimed is: 
     
       1. An aqueous dispersion consisting essentially of an emulsion polymer, wherein the emulsion polymer comprises a styrene/(meth)acrylate copolymer comprising from 70 to 99.7% by weight of one or more styrene and compounds selected from the group consisting of the acrylates and methacrylates of C 1  -C 12  monoalcohols,     from 0.3 to 10% by weight of compounds selected from the group consisting of α,β-monoolefinically unsaturated mono- and dicarboxylic acids, amides thereof, and N-substituted amides thereof, and     from 0 to 20% by weight of compounds selected from the group consisting of hydroxyl-containing monomers, acetylacetoxy-containing monomers, epoxide-containing monomers, monomers containing silane groups, nitrogen-containing monomers, and keto-containing monomers,      the percent by weight in each case based on the total weight of compounds used to form the polymer;     0.1 to 5% by weight based on the total weight of said emulsion polymer, of an emulsifier which is capable of enhancing the stability of said emulsion polymer with respect to polyvalent zirconium ions;   a water-soluble zirconium compound selected from the group consisting of ammonium zirconium carbonate, zirconium acetoacetate, zirconium acetate, sodium zirconium sulfate, zirconium propionate and potassium zirconium phosphate;   optionally, a zinc compound;   optionally, a chelating agent; and   optionally, one or more additives selected from the group consisting of film-forming auxiliaries, pigments, fillers, thickeners, dispersants, wetting agents, preservatives, and defoamers.   
     
     
       2. An aqueous dispersion as claimed in claim 1, wherein the zirconium compound is present in a quantity of from 0.2 to 20% by weight, calculated as ZrO 2 , based on the weight of the dispersion. 
     
     
       3. An aqueous dispersion as claimed in claim 1, wherein the zirconium compound comprises an ammonium zirconium carbonate complex. 
     
     
       4. An aqueous dispersion as claimed in claim 1, wherein said zinc compound is present in a quantity of from 0.1 to 10% by weight, based on the weight of the dispersion. 
     
     
       5. An aqueous dispersion of claim 1, wherein said zirconium compound is present as ZrO 2  in an amount from 1 to 5% by weight based on the weight of said polymer. 
     
     
       6. An aqueous dispersion as claimed in claim 1, wherein the emulsion polymer has a minimum film-forming temperature of from 0° to 50° C. 
     
     
       7. An aqueous dispersion as claimed in claim 1, wherein one or more of said additives selected from the group consisting of film-forming auxiliaries, pigments, fillers, thickeners, dispersants, wetting agents, preservatives, and defoamers are present. 
     
     
       8. A process for the preparation of an aqueous dispersion as claimed in claim 1, comprising mixing the emulsion polymer with the water-soluble zirconium compound and said emulsifier and optionally with one or more additives selected from the group consisting of film-forming auxiliaries, pigments, fillers, thickeners, dispersants, wetting agents, preservatives and defoamers, said emulsifier being present in an amount from 0.1 to 5% by weight based on the total weight of said emulsion polymer. 
     
     
       9. A process of claim 8, wherein said emulsifier is nonionic. 
     
     
       10. A process of claim 8, wherein said emulsifier is present in an amount from 0.5 to 1% by weight based on the weight of said polymer. 
     
     
       11. A process of claim 8, wherein said zirconium compound is present as ZrO 2  in an amount from 1 to 5% by weight based on the weight of said polymer. 
     
     
       12. An aqueous dispersion according to claim 1, wherein said aqueous dispersion consists of the emulsion polymer,   0.1 to 5% by weight based on the total weight of said emulsion polymer, of a nonionic emulsifier which is capable of enhancing the stability of said emulsion polymer with respect to polyvalent zirconium ions;   the water-soluble zirconium compound;   optionally, a chelating agent;   optionally, one or more additives selected from the group consisting of film-forming auxiliaries, pigments, fillers, thickeners, dispersants, wetting agents, preservatives, and defoamers.   
     
     
       13. A primer coating comprising an aqueous dispersion as claimed in claim 1. 
     
     
       14. A substrate coated with a coating as claimed in claim 13. 
     
     
       15. A substrate as claimed in claim 14, wherein the substrate before coating shows a tendency to bleeding. 
     
     
       16. A substrate as claimed in claim 14, wherein the primer coating is overcoated with another coating. 
     
     
       17. Wood coated with an aqueous dispersion as claimed in claim 1. 
     
     
       18. An aqueous dispersion as claimed in claim 1, which comprises ammonium tartrate as chelating agent. 
     
     
       19. An aqueous dispersion as claimed in claim 1, wherein the emulsion polymer comprises an acrylic polymer. 
     
     
       20. An aqueous dispersion as claimed in claim 1, which has a solids content of from 30 to 65% weight, and wherein the average particle diameter of the emulsion polymer is 0.02 to 1 μm, and which is substantially free of organic solvent. 
     
     
       21. A method of coating a substrate comprising coating a dispersion as claimed in claim 1 onto the substrate and coating a second coating onto the previously applied coating. 
     
     
       22. An aqueous dispersion of claim 1, wherein said emulsifier is nonionic. 
     
     
       23. An aqueous dispersion of claim 1, wherein said emulsifier is present in an amount from 0.5 to 1% by weight based on the weight of said polymer. 
     
     
       24. An aqueous dispersion consisting essentially of an emulsion polymer, wherein the emulsion polymer comprises a styrene/(meth)acrylate copolymer comprising from 70 to 99.7% by weight of styrene and compounds selected from the group consisting of the acrylates and methacrylates of C 1  -C 12  monoalcohols,     from 0.3 to 10% by weight of compounds selected from the group consisting of α,β-monoolefinically unsaturated mono- and dicarboxylic acids, amides thereof, and substituted amides thereof, and     from 0 to 20% by weight of compounds selected from the group consisting of hydroxyl-containing monomers, acetylacetoxy-containing monomers, epoxide-containing monomers, monomers containing silane groups, nitrogen-containing monomers, and keto-containing monomers,      the percent by weight in each case based on the total weight of compounds used to form the polymer;     
     
     
       0. 1 to 5% by weight based on the total weight of said emulsion polymer, of an emulsifier which is capable of enhancing the stability of said emulsion polymer with respect to polyvalent zirconium ions; a chelating agent;   a water-soluble zirconium compound selected from the group consisting of ammonium zirconium carbonate, zirconium acetoacetate, zirconium acetate, sodium zirconium sulfate, zirconium propionate and potassium zirconium phosphate;   optionally, a zinc compound;   optionally, one or more additives selected from the group consisting of film-forming auxiliaries, pigments, fillers, thickeners, dispersants, wetting agents, preservatives, and defoamers;   and, optionally, one or more protective colloids, initiators, reducing components, and regulators.   
     
     
       25. An aqueous dispersion according to claim 24, wherein said chelating agent comprises ammonium tartrate. 
     
     
       26. A process for the preparation of an aqueous dispersion as claimed in claim 24, comprising mixing the emulsion polymer with the water-soluble zirconium compound and said emulsifier, and optionally with one or more additives selected from the group consisting of film-forming auxiliaries, pigments, fillers, thickeners, dispersants, wetting agents, preservatives and defoamers, said emulsifier being present in an amount from 0.1 to 5% by weight based on the total weight of said emulsion polymer.